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  • 1.
    Grahn, Mattias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Faisal, Abrar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Lahore, Pakistan.
    Öhrman, Olov G.W
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. RISE ETC - Energy Technology Center, SE-941 28 Piteå, Sweden.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Signorile, Matteo
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Torino, Italy.
    Crocellà, Valentina
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Torino, Italy.
    Nabavi, Mohammad Sadegh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Small ZSM-5 crystals with low defect density as an effective catalyst for conversion of methanol to hydrocarbons2019In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308Article in journal (Refereed)
    Abstract [en]

    This work presents the synthesis of nearly defect-free ZSM-5 nanosized crystals, prepared in fluoride medium by seeding with silicalite-1. This material was carefully characterized and its catalytic performances in the methanol to hydrocarbons (MTH) reaction were assessed. Such fluoride-based material was compared to a reference ZSM-5, produced through a conventional alkaline synthesis but from the same seeding. Despite both the materials show closely identical morphology and they have a comparable acid site population, the catalyst prepared using the fluoride route showed significantly longer lifetime in MTH compared to the catalyst prepared using conventional synthesis at high pH. The slower deactivation for the samples prepared using the fluoride route was ascribed, thanks to a thorough in situ IR spectroscopy study, to its lower density of internal defects. According to the UV-Raman characterization of coke on the spent catalyst, the fluoride-based ZSM-5 catalyst produces less molecular coke species, most probably because of the absence of enlarged cavities/channels as due to the presence of internal defects. On the basis of these observations, the deactivation mechanism in the ZSM-5 synthesized by fluoride medium could be mostly related to the deposition of an external layer of bulk coke, whereas in the alkali-synthesized catalyst an additional effect from molecular coke accumulating within the porous network accelerates the deactivation process.

  • 2.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ye, Pengcheng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nabavi, Mohammad Sadegh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Selective blocking of grain boundary defects in high-flux zeolite membranes by cokin2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 16, p. 7295-7299Article in journal (Refereed)
    Abstract [en]

    Commercial application of zeolite membranes has been hindered by the challenge of preparing defect-free membranes. Herein, we report a facile method able to selectively plug grain boundary defects in high-flux MFI zeolite membranes by coking of iso-propanol at 350 °C. After modification, the permeance via defects was reduced by 70%, whereas that via zeolite pores was reduced by only 10%.

  • 3.
    Nabavi, Mohammad Sadegh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Stability of colloidal ZSM-5 catalysts synthesized in fluoride and hydroxide media2019In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 278, p. 167-174Article in journal (Refereed)
    Abstract [en]

    ZSM-5 zeolite crystals with carefully controlled thicknesses in the range 20–110 nm, i.e. in the colloidal domain, were synthesized in fluoride and hydroxide media. The crystals were treated in steam at high temperature to evaluate the stability and evaluated by SEM, XRD, NMR and NH3-TPD. The results showed that the framework of crystals synthesized in fluoride media was more stable than the framework of crystals synthesized in hydroxide media. This should be an effect of lower concentration of structural defects and silanol groups in the former zeolites as reported by other groups. However, independently of the synthesis conditions, all crystals dealuminated rapidly when treated with steam at the conditions investigated in the present work.

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